Reference for Numbers 10:4

וְאִם־בְּאַחַ֖ת יִתְקָ֑עוּ וְנוֹעֲד֤וּ אֵלֶ֙יךָ֙ הַנְּשִׂיאִ֔ים רָאשֵׁ֖י אַלְפֵ֥י יִשְׂרָאֵֽל׃

And if they blow but with one, then the princes, the heads of the thousands of Israel, shall gather themselves unto thee.